iio: adc: ad7124: support fractional sampling_frequency

Modify the attribute read/write functions for sampling_frequency and
filter_low_pass_3db_frequency to return fractional values.

These ADCs support output data rates in the single digits, so being
able to specify fractional values is necessary to use all possible
sampling frequencies.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dlech

drivers/iio/adc/ad7124.c

@@ -166,7 +166,6 @@ struct ad7124_channel_config {
 		bool buf_negative;
 		unsigned int vref_mv;
 		unsigned int pga_bits;
-		unsigned int odr;
 		unsigned int odr_sel_bits;
 		unsigned int filter_type;
 		unsigned int calibration_offset;
@@ -285,7 +284,17 @@ static u32 ad7124_get_fclk_hz(struct ad7124_state *st)
 	return fclk_hz;
 }
 
-static void ad7124_set_channel_odr(struct ad7124_state *st, unsigned int channel, unsigned int odr)
+static u32 ad7124_get_fadc_divisor(struct ad7124_state *st, unsigned int channel)
+{
+	/*
+	 * The output data rate (f_ADC) is f_CLK / divisor. We are returning
+	 * the divisor.
+	 */
+	return st->channels[channel].cfg.odr_sel_bits * 32 * 4;
+}
+
+static void ad7124_set_channel_odr(struct ad7124_state *st, unsigned int channel,
+				   unsigned int odr, unsigned int odr_micro)
 {
 	unsigned int fclk, factor, odr_sel_bits;
 
@@ -300,29 +309,28 @@ static void ad7124_set_channel_odr(struct ad7124_state *st, unsigned int channel
 	 * FS[10:0] can have a value from 1 to 2047
 	 */
 	factor = 32 * 4; /* N = 4 for default sinc4 filter. */
-	odr_sel_bits = clamp(DIV_ROUND_CLOSEST(fclk, odr * factor), 1, 2047);
+	odr_sel_bits = DIV_ROUND_CLOSEST(fclk, odr * factor +
+					       odr_micro * factor / MICRO);
+	odr_sel_bits = clamp(odr_sel_bits, 1, 2047);
 
 	if (odr_sel_bits != st->channels[channel].cfg.odr_sel_bits)
 		st->channels[channel].cfg.live = false;
 
-	/* fADC = fCLK / (FS[10:0] x 32) */
-	st->channels[channel].cfg.odr = DIV_ROUND_CLOSEST(fclk, odr_sel_bits *
-								factor);
 	st->channels[channel].cfg.odr_sel_bits = odr_sel_bits;
 }
 
-static int ad7124_get_3db_filter_freq(struct ad7124_state *st,
-				      unsigned int channel)
+static int ad7124_get_3db_filter_factor(struct ad7124_state *st,
+					unsigned int channel)
 {
-	unsigned int fadc;
-
-	fadc = st->channels[channel].cfg.odr;
-
+	/*
+	 * 3dB point is the f_CLK rate times some factor. This functions returns
+	 * the factor times 1000.
+	 */
 	switch (st->channels[channel].cfg.filter_type) {
 	case AD7124_FILTER_FILTER_SINC3:
-		return DIV_ROUND_CLOSEST(fadc * 272, 1000);
+		return 272;
 	case AD7124_FILTER_FILTER_SINC4:
-		return DIV_ROUND_CLOSEST(fadc * 230, 1000);
+		return 230;
 	default:
 		return -EINVAL;
 	}
@@ -346,7 +354,6 @@ static struct ad7124_channel_config *ad7124_find_similar_live_cfg(struct ad7124_
 				     bool buf_negative;
 				     unsigned int vref_mv;
 				     unsigned int pga_bits;
-				     unsigned int odr;
 				     unsigned int odr_sel_bits;
 				     unsigned int filter_type;
 				     unsigned int calibration_offset;
@@ -363,7 +370,6 @@ static struct ad7124_channel_config *ad7124_find_similar_live_cfg(struct ad7124_
 		    cfg->buf_negative == cfg_aux->buf_negative &&
 		    cfg->vref_mv == cfg_aux->vref_mv &&
 		    cfg->pga_bits == cfg_aux->pga_bits &&
-		    cfg->odr == cfg_aux->odr &&
 		    cfg->odr_sel_bits == cfg_aux->odr_sel_bits &&
 		    cfg->filter_type == cfg_aux->filter_type &&
 		    cfg->calibration_offset == cfg_aux->calibration_offset &&
@@ -718,16 +724,23 @@ static int ad7124_read_raw(struct iio_dev *indio_dev,
 
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		mutex_lock(&st->cfgs_lock);
-		*val = st->channels[chan->address].cfg.odr;
+		*val = ad7124_get_fclk_hz(st);
+		*val2 = ad7124_get_fadc_divisor(st, chan->address);
 		mutex_unlock(&st->cfgs_lock);
 
-		return IIO_VAL_INT;
-	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
-		mutex_lock(&st->cfgs_lock);
-		*val = ad7124_get_3db_filter_freq(st, chan->scan_index);
-		mutex_unlock(&st->cfgs_lock);
+		return IIO_VAL_FRACTIONAL;
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY: {
+		guard(mutex)(&st->cfgs_lock);
 
-		return IIO_VAL_INT;
+		ret = ad7124_get_3db_filter_factor(st, chan->address);
+		if (ret < 0)
+			return ret;
+
+		/* 3dB point is the f_CLK rate times a fractional value */
+		*val = ret * ad7124_get_fclk_hz(st);
+		*val2 = MILLI * ad7124_get_fadc_divisor(st, chan->address);
+		return IIO_VAL_FRACTIONAL;
+	}
 	default:
 		return -EINVAL;
 	}
@@ -744,10 +757,10 @@ static int ad7124_write_raw(struct iio_dev *indio_dev,
 
 	switch (info) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
-		if (val2 != 0 || val == 0)
+		if (val2 < 0 || val < 0 || (val2 == 0 && val == 0))
 			return -EINVAL;
 
-		ad7124_set_channel_odr(st, chan->address, val);
+		ad7124_set_channel_odr(st, chan->address, val, val2);
 
 		return 0;
 	case IIO_CHAN_INFO_SCALE:
@@ -1296,7 +1309,7 @@ static int ad7124_setup(struct ad7124_state *st)
 		 * regardless of the selected power mode. Round it up to 10 and
 		 * set all channels to this default value.
 		 */
-		ad7124_set_channel_odr(st, i, 10);
+		ad7124_set_channel_odr(st, i, 10, 0);
 	}
 
 	ad7124_disable_all(&st->sd);